Where does “thoughtless” come from?

Thoughtless derives from Old English lēas, meaning "without" or "lacking," combined with thought, ultimately tracing through Proto-Indo-European lewH- and teng-.

thoughtless (English): Marked by or showing lack of due thought or care;...

Definitions

  1. Marked by or showing lack of due thought or care;...

Ancestry of “thoughtless”, step by step

StepLanguageWordMeaning
1English-less(something); without (something). Added usually to a noun to form an adjective signifying a lack of that noun
2Middle English-lesLacking (something); without (something)
3Turkish-lewith, shortened form of ile; by, shortened form...
4Turkishilewith; and
5Ottoman Turkishایلهby
6Old Anatolian Turkishاِیلَه
7Proto-Turkicbilewith, together, also

Words derived from “thoughtless

Every word from Proto-Turkic bile
thoughtless — Etymology, Origin & Word History | Etymology Explorer